1. Field of the Invention
The present invention relates to a joint body of a ceramic member and a metal member and a method of producing the same.
2. Description of Related Art
A method of directly connecting substrates made of aluminum nitride sintered body is known. For example, in Japanese Patent Laid-Open Publication No. 2-124778 (JP-A-2-124778), aluminum nitride substrates were heated to a temperature of 1800xc2x0 C.-1900xc2x0 C., and connected integrally by means of a diffusion connection. Moreover, in Japanese Patent Laid-Open Publication No. 8-13280 (JP-A-8-13280), an aluminum nitride joint body having a relatively high strength is disclosed.
Moreover, a method of brazing one nitride ceramic member to another nitride ceramic member is also known. For example, in Japanese Patent Laid-Open Publication No. 8-277171 (JP-A-8-277171), a joint body having a high anti-corrosive property with respect to halogen series corrosive gas such as CIF3 and so on is obtained by connecting aluminum nitride members by using a brazing material consisting of aluminum, copper or nickel as a main ingredient and an active metal such as titanium as an additive. Such a brazing material is hard to corrode by halogen series corrosive gases and easily wets the surface of aluminum nitride.
However, when a cylindrical metal member is brazed to a flat or a plate-like ceramic member, the following problems were found. For example, in the field of semiconductor manufacturing, the present inventors tried to connect a ring-shaped support member made of KOVAR (Fexe2x80x94Nixe2x80x94Co alloy) to a rear surface of a suscepter for supporting a semiconductor wafer made of aluminum nitride sintered body. However, since the area of the suscepter becomes larger corresponding to an increase of silicon wafer diameter, it is extremely difficult to connect the ring-shaped support member to the suscepter under such a condition that they are correctly aligned. Particularly, when the rear surface of the suscepter is not sufficiently flat, or when the rear surface of the suscepter is not parallel, i.e., slightly aligned, to an end surface of the ring-shaped support member, the distance between the rear surface of the suscepter and the end surface of the ring-shaped support member is locally very small. Therefore, there is a tendency such that the thickness of the brazing layer between the suscepter and the ring-shaped support member becomes smaller. In this manner, if the thickness of the brazing layer between the rear surface of the suscepter and the end surface of the ring-shaped support member becomes locally thin, a thermal strain generated between the suscepter and the ring-shaped support member cannot be absorbed, so that it causes local crack generation.
Moreover, when the ring-shaped support member is an iron based metal, such as KOVAR, stainless steel and so on, a reaction layer such as an intermetallic compound is precipitated due to a reaction between the brazing member and the ring-shaped support member, and the durability and the hardness of the brazing member are increased. As a result, the remaining stress generated in the suscepter and the ring-shaped support member becomes larger.
An object of the invention is to provide a joint body of a ceramic member and a cylindrical metal member in which a metal connection portion having a predetermined thickness along all connection regions between an end portion of the metal member and the ceramic member can be formed. Moreover, an object is also to prevent the deterioration of a portion of the metal connection portion which is particularly contacted to the ceramic member and to prevent an increase of a durability or a hardness of the metal connection portion.
Further, another object of the invention is to provide a joint body of a ceramic member and a cylindrical metal member, which is strong for a heat cycle and is hardly to generate a local crack.
According to the invention, a joint body of a ceramic member and a cylindrical metal member, comprises a structure such that:
(1) an end portion of the metal member and the ceramic member are connected via a metal connection portion;
(2) the metal connection portion has a metallized layer formed on the ceramic member and a brazing connection portion interposing at least between the metallized layer and an end portion of the metal member; and
(3) a melt point of a brazing member constructing the brazing connection portion is lower than that of a brazing member constructing the metallized layer.
The inventors thought a method of forming at first a metallized layer on the ceramic member, interposing a brazing member for connection between the metallized layer and an end portion of the metal member, melting the brazing member for connection at a temperature lower than a melt point of a brazing member for metallizing, generating a brazing connection portion at least between the metallized layer and an end portion of the metal member. In the joint body thus obtained, when an end portion of the metal member and a connection surface of the ceramic member are inclined with respect to predetermined relative positions, or even when the distance between the ceramic member and the metal member becomes locally small during brazing (since the flatness of an end portion of the metal member and the flatness of the connection surface of the ceramic member are low), it is possible to keep the metal connection portion having a predetermined thickness by means of the metallized layer.
Further, since the melt point of the brazing connection portion is low, it is possible to prevent the reaction of the metallized layer and the metal member, and to suppress the increase of the durability or the hardness of the metallized layer after connection.
Moreover, in the present invention, since a metal plate made of a low durability metal or a low thermal expansion metal is interposed between the end portion of the cylindrical metal member and the connection surface of the ceramic member, it is possible to obtain a metal connection portion having a predetermined thickness along all the connection regions.